This application relates to a blade dovetail for a gas turbine engine.
Gas turbine engines may be provided with a fan for delivering air to a compressor section. From the compressor section, the air is compressed and delivered into a combustion section. The combustion section mixes fuel with the air and burns the combination. Products of the combustion pass downstream over turbine rotors which are driven to rotate and in turn rotate the compressor and fan.
The fan may include a rotor having a plurality of blades.
One type of fan blade is a generally hollow fan blade comprised of two or more pieces. The blades are subject to a number of challenges, including internal stresses that vary along the length of the fan blade.
Known fan blades typically include an airfoil extending radially outwardly of a portion known as a dovetail. The dovetail sits within a slot in the rotor. As the fan rotates, centrifugal force urges the blade radially outwardly. As this occurs, the dovetail is urged against surfaces of the rotor. In instances where the rotor is formed of a stronger material than the dovetail, this can result in the circumferential edges of the dovetail bending downwardly, and bowing a bottom surface of the dovetail upwardly. Known dovetails have had a relatively flat bottom, and this can result in distortion of the dovetail when under load.
Historically, the fan rotor has been driven by a direct connection to a turbine section. However, more recently, a gear reduction has been incorporated between the turbine section and the fan rotor. The turbine section allows the fan to rotate at slower speeds relative to the turbine. With the change in the fan speed, it has been possible to make the fan blades larger. The distortion above can increase as the fan blade becomes larger.